In general, a motor vehicle, such as a sedan, is equipped with a hand brake (parking brake) for use in causing the motor vehicle to remain stationary in a place where the motor vehicle is parked. It happens at times that a car driver has to park the car in a place and to leave for a moment to take care of the chores, leaving behind an accompanying child or children in the car. In the absence of an adult's supervision, the accompanying child or children may release the hand brake of the car accidentally or playfully. Such an incident can often bring about a serious accident, especially when the car in question is parked in a sloped place. Nowadays the car makers are required by law to equip the cars with a safety device capable of preventing the hand brake of a motor vehicle from being released accidentally by a child.